Suppression of spectral anomalies in SSFP-NMR signal by the Krylov Basis Diagonalization Method

Moraes, Tiago Bueno; Santos, Poliana M.; Magon, Cláudio José; Colnago, Luiz Alberto

doi:10.1016/j.jmr.2014.03.009

Cited by 6 publications

(3 citation statements)

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“…The echo signal appearing at time 2τ was integrated in a 148 ns time window and two scans were added for signal averaging. The resulting ESEEM data were processed as follows: (1) the modulated echo decay was first processed by the Krylov Basis Diagonalization Method (KBDM) to isolate the zero (or low) frequency decay component; (2) for further analysis, this zero frequency component was fitted to an exponential decay function, as will be described later herein; (3) the KBDM‐edited low frequency component was subtracted from the experimental signal in order to leave behind the pure decaying modulation; and (4) the modulation decay was Fourier‐transformed, resulting in the ESEEM spectrum. The echo‐detected field‐sweep absorption spectra, EDFS, were recorded using a similar two‐pulse sequence.…”

Section: Methodsmentioning

confidence: 99%

Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass‐ceramics

et al. 2017

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This paper describes the preparation of a transparent glass‐ceramic from the SiO2‐K2O‐ZnO‐Al2O3‐TiO2 system containing a single crystalline phase, gahnite (ZnAl2O4). TiO2 was used as a nucleating agent for the heat‐induced precipitation of gahnite crystals of 5‐10 nm. The evolution of the ZnAl2O4 spinel structure through the gradual formation of Al‐O bonds was examined by infrared spectroscopy. The dark brown color of the transparent precursor glass and glass‐ceramic was eliminated using CeO2. The increase in transparency of the CeO2‐doped glass and glass‐ceramics was demonstrated by UV‐visible absorption spectroscopy. EPR measurements confirmed the presence of Ce3+ ions, indicating that CeO2 was effective in eliminating the brown color introduced by Ti3+ ions via oxidation to Ti+4. The hardness of the glass‐ceramic was 30% higher than that of the as‐prepared glasses. This work offers key guidelines to produce hard, transparent glass‐ceramics which may be potential candidates for a variety of technological applications, such as armor and display panels.

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Section: Methodsmentioning

confidence: 99%

Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass‐ceramics

et al. 2017

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“…Therefore, in the SSFP regime, each pulse produces FID and echo signals that are 180 out of phase. SSFP sequences have been widely used in fast magnetic resonance imaging protocols as well as to enhance the signal-to-noise (SNR) ratio in high-resolution NMR spectroscopy [15][16][17][18][19]. Figure 1c shows the SSFP signal observed in a very fast pulse rate in which T p < T 2 * .…”

Section: Steady-state Free Precession Sequencesmentioning

confidence: 99%

Food Analysis Using Fast Steady-State Free Precession TD-NMR Relaxometric Methods

Colnago

Moraes

Monaretto

2016

Modern Magnetic Resonance

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The importance of NMR relaxometry in food analysis has been growing at a fast pace in recent years. Most food-related applications rely upon the transverse relaxation time (T 2) that can be measured with a single-shot method using the Carr-Purcell-Meiboom-Gill pulse sequence. On the other hand, the longitudinal relaxation time (T 1) has been seldom used due to the long measurement time of classical methods (e.g., inversion recovery, saturation recovery, and other pulse sequences). To bypass the long acquisition time, several single-shot, steady-state methods have been proposed to measure T 1 , T 2 , and T 1 /T 2 ratio. This chapter presents and discusses the advantages and disadvantages of rapid, single-shot continuous wave free precession (CWFP) pulse sequences in the measurement of

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“…The QFT method was based on a small variation in frequency offset. Although these procedures minimize these anomalies, SSFP sequences were not routinely used in high resolution NMR.We revised these methods and suggested some modifications to increase the applications of SSFP in high-resolution NMR using the Traff apodization function [5] to minimize the truncation problem, or processing the SSFP time domain signal with a parametric method based on Krylov Basis Diagonalization Method (KBDM) [6]. KBDM solves the truncation and phase anomalies but not the amplitude problem.…”

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confidence: 99%

Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

2019

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This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval T p shorter than the effective transverse relaxation time (T 2 *), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T 1 . Therefore, T p should be as short as possible (limited by hardware). For T p < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T 1 /T 2 ; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T 1 using a low flip angle (5 • ) or T 2 , using θ = 180 • . For measuring T 1 and T 2 simultaneously in a single experiment, it is necessary to use θ = 90 • , the values of T* and M 0 , and the magnitude of CWFP signal |M ss |. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T 2 . The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.to suppress these anomalies using a small variation of T p that cancels the echo component. In the same year, Schwenk [4] proposed the Quadriga Fourier Transform (QFT) to suppress these anomalies. The QFT method was based on a small variation in frequency offset. Although these procedures minimize these anomalies, SSFP sequences were not routinely used in high resolution NMR.We revised these methods and suggested some modifications to increase the applications of SSFP in high-resolution NMR using the Traff apodization function [5] to minimize the truncation problem, or processing the SSFP time domain signal with a parametric method based on Krylov Basis Diagonalization Method (KBDM) [6]. KBDM solves the truncation and phase anomalies but not the amplitude problem. Therefore, SSFP sequences cannot be used to efficiently enhance signal to noise ratio (SNR) in high-resolution NMR. SSFP sequences have been successfully used in magnetic resonance imaging [7,8] and in low-field, time-domain NMR [9][10][11]. The use of a SSFP sequence in low field time domain (TD-NMR) started in year 2000 [12,13]. The applications of SSFP sequences in TD-NMR can be performed under the drastic condition where T p < 1 ms. Under this condition, a truly continuous wave free precession (CWFP) regime is obtained [13]. Normally, CWFP sequences use T p < 0.5 ms, as T p has to be shorter than T 2 *, which is in the order of 1 ms in most TD-NMR spectrometers.In the CWFP regime, F...

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Suppression of spectral anomalies in SSFP-NMR signal by the Krylov Basis Diagonalization Method

Cited by 6 publications

References 20 publications

Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass‐ceramics

Crystallization, mechanical, and optical properties of transparent, nanocrystalline gahnite glass‐ceramics

Food Analysis Using Fast Steady-State Free Precession TD-NMR Relaxometric Methods

Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

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